Among the conventionally-known vehicle side body structures are ones where a side sill in the form of a rectangular cross-sectional pipe, constituting a lower frame section of a door opening, is fixedly joined with a center pillar constituting a vertical frame section between front and rear door openings of the vehicle. The side sill comprises four panels fixedly joined together along their edge portions; the four panels are, in an outer-to-inner direction of the vehicle, an outside outer panel, an inside outer panel, an inside inner panel and an insidemost inner panel located inwardly of the inside inner panel. Further, in a joint section of the structure where the center pillar is fixedly joined to the side sill, a partitioning member (bulkhead or load transmitting member) is provided in a space defined by the inside outer panel and the inside inner panel, to thereby increase a mechanical strength against a lateral collision of the vehicle. One example of such vehicle side body structures is disclosed in Japanese Patent No. 3492922 (hereinafter referred to as “relevant patent literature”).
However, in the vehicle side body structure disclosed in the relevant patent literature, provision of the partitioning member (bulkhead or load transmitting member), extending all the way from the inside outer panel to the insidemost inner panel, would invite undesirable interference between the load transmitting member and the inside inner panel (and hence a passed-through section of an inner center pillar member), although a lateral collision impact (load) can be transmitted via the load transmitting member to a vehicle floor connecting to the insidemost inner panel.
Further, because the vehicle side body structure disclosed in the relevant patent literature is constructed in such a manner that, when a lateral collision impact (load) has been input to the door, the lateral collision impact is absorbed by the door and center pillar, and as a consequence, the vehicle body would be undesirably reduced in mechanical strength.